1. Field of the Invention
The present invention relates to an antenna, and in particular to a multi-band printed monopole antenna employed in a mobile electronic device.
2. Description of the Prior Art
The development of wireless local area network (WLAN) technology has been attended by the development of devices operating under the IEEE 802.11b standard (in the 2.45 GHz band) and the IEEE 802.11a standard (in the 5.25 GHz band). These devices benefit from a multi-band antenna.
In order to minimize the size of an antenna and permit multi-band operation, multi-band monopole antennas have been developed for use with certain communication applications. More specially, U.S. Pat. No. 6,100,848 discloses a multi-band printed monopole antenna including a ground plane, a printed circuit board (PCB) 12, a conductive trace 18 and a parasitic element 20 respectively formed on the opposite sides of the PCB 12. The conductive trace 18 has an electrical length in which primary resonance occurs within a first frequency band. The parasitic element 20 is coupled to the conductive trace 18 but not directly connected to tune the conductive trace 18 to a secondary resonance within a second frequency band. However adding a parasitic element 20 will add manufacturing cost to the antenna. Furthermore, putting the parasitic element on the opposite side will also add complexity to manufacturing.
Hence, an improved multi-band antenna is desired to overcome the above-mentioned disadvantages of the prior art.
A primary object, therefore, of the present invention is to provide a simple multi-band printed monopole antenna for operating in different frequency bands.
A multi-band printed monopole antenna in accordance with the present invention for an electronic device includes a substrate, a radiating element formed on a surface of the substrate comprising a first and second radiating patches and a first and second connecting patches, a ground portion beside the radiating element and a feeder cable. The radiating element is in a rectangular window shape with a gap in one side. The ground portion comprises a long conductive patch parallel to the first radiating patch and a short conductive patch. The long conductive patch is near to the first radiating patch. The coupling between the first radiating patch and the long conductive patch occurs a first resonance within a first frequency band. The second radiating patch occurs a second resonance in a second frequency band.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of a preferred embodiment when taken in conjunction with the accompanying drawings.